1. Field of the Invention
The present invention relates generally to thermally expandable baffles for sealing cavities in vehicles. More particularly, the inventive baffles include a quantity of thermally expandable sealing material and a support for the material which maintains the baffle in the desired location within the cavity until the material is thermally expanded so as to contact the walls forming the cavity, thus sealing the cavity.
2. Description of the Prior Art
During the fabrication of automobiles, trucks, and similar over-the-road vehicles, many body components present structural members having cavities that require sealing to prevent the entrance of moisture and contaminants which can cause corrosion of the body parts. It is also necessary to stabilize these members in order to attenuate noise that would otherwise be transmitted along the length or passage of the cavity. For example, the upright post structure or pillar of a vehicle body defining a portion of a respective window opening presents an elongated passage or cavity which can collect moisture and contaminants. Furthermore, this cavity can also transmit annoying sounds unless the cavity is at least partially filled with a sealant material. However, many of these cavities are irregular in shape or narrow in size, thus making them difficult to properly seal and baffle.
Many attempts have been made to seal these cavities, including spraying sealants into the cavity, introducing foam products into the cavity, and using fiberglass matting and the like. These methods each have drawbacks. For example, foaming in place presents a problem in that it is difficult to control where the foam travels upon its introduction into the cavity. Furthermore, it is often necessary to introduce an excess amount of foam into the cavity in order to ensure that the cavity is sufficiently sealed. Finally, foams will generally not adhere to the interior surfaces of the cavity walls if those surfaces contain even a small amount of oil.
Self-sustaining foam products, either with or without a non-foam support structure, have been introduced into structural member cavities in an attempt to seal the cavities. However, these methods generally result in the addition of excess weight to the structural member which is undesirable in most instances. Attempts have been made to utilize foam products which are lighter in weight or which do not use a support structure. However, these attempts have generally resulted in products which lack the necessary sealing and baffle abilities.
Finally, other types of foam or foamable products are tacky in nature, and thus cannot readily be positioned at the exact required location in the selected cavity. Such products also present unique packaging problems to the manufacturer and require special handling during installation.
The instant invention overcomes these problems by providing a thermally expandable baffle for sealing a cavity (such as one in a pillar or rail of a vehicle) at a predetermined location within the cavity.
In more detail, the baffle includes a quantity of thermally expandable sealing material and a support for maintaining the expandable material in the desired location within the cavity until the material is expanded. The sealing material is preferably a synthetic resin material and expands when subjected to temperatures achieved at specific points in the vehicle manufacturing process (e.g., during the paint bake stage of the process). Thus, the expansion temperature of the material should be at least about 149xc2x0 C.
The support for the material is formed of a material having a melting point higher than the expansion temperature of the sealing material (such as nylon). Preferably, the support comprises a pair of spaced-apart walls defining a space therebetween for depositing of the sealing material therein. The walls are joined at one end by a common end wall, and are secured adjacent the other end by a connecter rod passing between and secured to the walls. The support also includes a fastener for attaching the baffle to a cavity wall. Preferably, the entire support is integrally constructed.
In use, the inventive baffle is placed within the cavity at the desired location by inserting the fastener into an opening on the cavity wall. Once the baffle is in position, various other manufacturing processes can be conducted without adversely affecting the baffle. When the vehicle is heated to the expansion temperature of the sealing material, the material will expand outwardly from the baffle towards the cavity walls, causing the expanded material to adhere to, and essentially seal, the cavity walls.